In the course of completing an oil and/or gas well, a string of protective casing can be run into the wellbore followed by production tubing inside the casing. The casing can be perforated across one or more production zones to allow production fluids to enter the casing bore. During production of the formation fluid, formation sand may be swept into the flow path. The formation sand tends to be relatively fine sand that can erode production components in the flow path. In some completions, the wellbore is uncased, and an open face is established across the oil or gas bearing zone. Such open bore hole (uncased) arrangements are typically utilized, for example, in water wells, test wells, and horizontal well completions.
Since produced sand is undesirable, a variety of completion techniques have been utilized to address the problem. For example, sand control screens have been utilized to control sand production. However, in addition to the sand control screens, other wells use a gravel pack placed around the screens, which essentially acts as a filter to reduce the amount of fine formation sand reaching the screen, thus controlling sand production. To obtain a complete gravel pack, it is often preferred to fully pack an annulus external to the production tubing across a sand face or external to a sand screen without leaving any voids. Failure to obtain a complete gravel pack can result in lower productivity and/or a sand-producing gravel pack.
Some sand control screens utilize inflow control devices to provide a uniform pressure differential between the flowstream in the tubulars and the reservoir. As a result, a uniform drawdown of fluid along the completion interval is achieved. By using inflow control devices, the reservoir inflow from a high productivity zone can be reduced while improving inflow from a low productivity zone.
However, inflow control devices installed in line with a screen often impede packing of the gravel fully along the length of the screen. Inflow control devices limit the flow rate at which the gravel pack can be pumped, since the flow rate of returns is the same as the flow rate pumped. During gravel packing, the carrying fluid must be removed from the gravel slurry to allow packing of the gravel around the screen. The fluid in the pumped gravel slurry typically follows along the path of least resistance. Thus, the gravel pack liquid flow tends to seek passage through the screen in close proximity to the inflow control device port, thus causing an accumulation of gravel near the port. Once the fluid flow resistance through the gravel accumulating near the port is greater than the fluid flow friction required for flow to enter the next path of lower resistance, the packing process may cease at the prior port and skip to the next port. Often the result is that part of the screen does not have a sufficient gravel pack to the filter formation solids, thus resulting in an incomplete gravel pack.
Accordingly, there is a need in the art for a gravel pack assembly and method which provides the pressure-balancing advantages of an inflow control device, while also providing the fluid flow necessary to form a complete gravel pack.